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Jan. 22, 1924. 1,481,586 W. A. BENSON WIRE CHIEFS TEST CIRCUITS FOR TELEPHONE SYSTEMS Filed Feb. '7. 1921 6 Sheets-SheeI l raund JTM/'Zar Sounder;

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w. A. BENSQN WIRE CHIEFS TEST CIRCUITS FOR TELEPHONE SYSTEMS Filed Feb. 17. 1921 6 Sheets-Sheet 2 Saum/er )fe/ease -:3:5

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Jan. `122, 1924. 1,481,586

W. BENSON AWIRE CHIEFS TEST CIRCUITS FOR TELEPHONE SYSTEMS Filed Feb. 17. 1921 Irl" ham HEEL-Leim Jan.l22, 1924.

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v Mews/AML 1111591 H BEUSE/n W. A. BEINSQN WIRE CHEF'S TEST CIRCUITS FOR TELEPHONE SYSTEMS YFiledreb- 17, 1921 s sheets-sheet Jan. 22, 1924. 1,481,586

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Application lilcd February 17, 192i.

Q 'o all fai/tom may conce/n lle it lrnown that l, Vtrnnnmr it.. BENSON,

a citizen oi the United bltates or America,

and resident or hicago, (look County, and 5 Stat@ ot illinois, have invented certain new and useful Improvements in idf ire (,hiets7 Test Circuits :lor Telephone blystems, ot which the iollowing :is a specification.

The present invention relates in general to wire chiefs test circuits :tor telephone sysi tenis, but more especially to test circuits oit this kind which are adapted ior use in automatic telephone systems; and the object oit the invention brietly stated is revision and 15 rearrangement ol the circuits and the addition ot certain new features whereby all the various tests to which a subscribers line may be subjected can be performed accurately and with the maximum facility. The apparatus employed, and the various features oi? the invention will be described 'fully hereinafter, reference beingl had to the accompanying drawings, in which the system is illustrated by means ot the usual circuit dia grains.

Referring to the drawings, in orner to enable the circuits to be readily understoodthe six sheets should he arranged as shown in Fig. 'l'. When laid out in this manner it will be perceived that Figs. l to lf, inclusive, show the test circuits proper, together with the necessary auxiliary apparatus, which are located at the wire chiets deslr; while Figs. i and (S show the circuits or three automatic switches known respectively as a test dis tributor, a test connector selector, and a test connector', which are used ior connecting;` the test -circuit to any suhscribei"s line which 'it is desired to test.

.1o From an inspection ot the v'irst tour sheets .fi testing devices and keys are duplicated inthe two tests circuits, it may be stated that in general the primarytest circuit is used for making the regular routine tests, and especially 'for all tests which require the use ot s.; the volt meter, while the secondary test cir- Serial No. 445,?10.

cuit is used lor those tests which require a considerable length ot time to perform, and which do not require the use of the volt meter.

'lo provide :for connecting` the test circuits with subscribers lines, which .it is desired to test, the wire chiefs position is equipped with a number of outgoing` test trunk aclts such as the jack J Fig. l). The jaclr l is the terminal ot a trunk line which extends by way oi the test trunk relay equipment M to the test distributor switch D. rlest distributor B is a vertical and rotary switch of the well known tltrowger type, having l0() sets oi? bank contacts arranged in l0 horizontal rows, or levels. ln addition to the usual operating magnets and controlling relays, the switch is provided with a side switch controlled bythe well known private magnet, which is 'For the purpose or' altering;` the cir cuits alter each series of controlling' iinpnlscs is received. The switch circuits are shown complete, and will be described in full hereinafter. Y

'lhe test connector selector E, Fig. 6, is a switch oit' the Strowger type also, but differs trom the test distributor D principally in having;` only a single level of bank contacts. It will be understood from this that the switch has a rotary movement only, and that the vertical magnet and those parts which have to do only with the ven tical movement oit the switch may be omitted. lt may be mentioned also that the oii normal spring 113 is arranged so that it will he shii'ted on the first rotary slop ot the switch rather than on a vertical step, as is usually the case. The test con-- hector ll is also a llltrowger vertical and rotary switch, has the itull l0() contact sets, and so 'tar its mechanical construction is concerned is similar to the test distributor D. The side switch is omitted, however, and the circuits are wry much simplified in accordan e with the simpler functions which the switch has to perform.

lt will be understood that the subscribers lines in the system are divided into groups or' l0() lines each in accordance with the capacity of the connector switches, which are ordinarily used ior completing local connections. ln every 100 line unit, in addition to the l() or l2 local connectorswhich are ordinarily provided, there is one test connector such as the test connector H, the

Aintervening switches.

latter connector switch being exclusively for the use of the wire chief in testing the subscribers lines. One `of the subscribers lines of the group, to which the connector H belongs, is shown at the extreme right of Fig. G, and extends to the automatic telephone substation A. The reference character C indicates an individual line switch of the well known rotary type, which is provided for the use of the subscriber at substation A in extending his line, when calling, to an idle first selector switch in the regular exchange trunling system.

The arrangement of the trunking between Jthe testswitches `will now be explained a little more lully. lt we assume a fr digit system oil? 10000 ,lines capacity, there will be 100 groups of connector' switches, and as a test connector is provided in each of these groups there will be 1.00 test connectors. New, since the test distributors have 100 Vcontact sets and are directi-vely controlled in both their vertical and rotary movements,

'allot these test connectors may be reached by way of the test distributors without any This is the usual arrangement for a straight 4 digit system. There will be perhaps three or tour ot' the test distributors such as the test distributor D, Fig. 5, which have common access to all oit the test connectors inthe various groups.

VIt happens quite often, however, that in systems which include a number of party lines, in addition to the individualY or private "lines, third selectors are inserted between the second selectors and connectors in those major groups of the system which are used Vfor the party line trattic. The party line subscribers are then called by `means of tive digits, instead of four, the

extra digit beine the third which controls the operation or the third selectors in selecting the proper group of connectors. The drawing shows an arrangement ot test switches 4which is adapted for use 1n a composite system of the type described, which includes both individual and party lines. The test distributors have direct. access to all of the test connectors which are located in the individual line connector groups, but on the particular level, or possibly levels, which are assigned to the party lines, the test distributors have access to test connector selectors such as the test connect-or selector E, which is shown in Fig. 6. It is noted in thisconnection that the contacts in the party line level are not multipled be tween the several test distributors, but a trunk line extends trom each contact set Vto a separate connector selector. For instance, considering the first contact set in the eighth level, if this contact set corresponds to a party line group, which we may assume to be the case, it is. not multipled between the several test distributors but a separate trunk line extends from this contact set .in cach test distributor to a dil' ferent test connector selector. The test con nector selectors with correspond to the saine numbered contact sets in the test distributors have their banks connected in multiple and have connnon access to the test con` nectors in ten different connector groups.

Having described the system generally. the operation of the circuits will now be cxplained more in detail, and a description will first be given ol the procedure followed in connecting one of the test circuits. say the primary test circuit, willi a subst-rilons` line. Assuming that it is desired to test the line of substation A, Fig. (l, the telephone nuni`V ber ot which is 45078, the wir chici" lirsl operates thc calling device key l). and then inserts the primary plug in the jack of an idle outgoing` test trunk, which we will assume the test trunk shown at the lclt of Fig. 5. When the plug is inserted in tlu` jack, a circuit is completed for the busy lanrp L which is inultipled at other tcst positions, and the glowing of the busy lamps irulicales to the other testers that this particular trunk is in use. lVhen the calling device key is operated, the calling device t5, Fig. Il., is con nected across the tip and ring conductors of the test circuit and since these conductors have been extended to the heavy test conductors 9 and ll. of the test trunk by the insertion of the'` plug in the jack, the rclays 3l and 33 ot' the test distributor D will be energized in series. These rela-ys close av circuit for the slow acting release relay 32 which, upon energizing, grounds the con ductor l0 at its armature 52, thus closingr the circuit ot the busy lamps at a new point. Relay 32 also breaks the release circuit at its armature 53 and at the same armature prcpares a circuit for the vertical magnet Ll-l in the usual manner. It will bc noticed that the lower winding` of the electro-polarizcil relay 202 is included in the tip side ol,l the line at the test circuit'. lclay 302 in not op erated, however, since a circuit has already been closed at the callingr device ltcy l'or ils upper polarizing winding. The wo windings are so connected that at his time their magnetizing etlects oppose each other and the relay accordingly remains iinnicraiive.

The calling device dial may now bc operated in accordance with the trst digit ot the desired number, which is the digit l. .i\s a result a series o tour interruptions pro` duced in the circuit ol relays 3l and ll. and both of these relays accordingly decucrgize momentarily tour times. Relay 3l. at cach deenergization, transmits an impulse ofi current to the vertical magnet l-l over a path which may be traced from grouinl by way of armature 50 and its resting contact, armature 53 and its working contact, the winding ot' the slow acting series relay 54, winding,r oi' lil idleness. .1

the vertical magnet il., and the side switch wiper l-, in first position, to battery. By the operation of the vertical magnet, the switch wipers TO, inclusive, are raised step by step until 'they stand opposite the :tourth level oit bankcontacts. Relay Sei energized in series with the vertical magnet, and being slow act-ing retains its armature in operate .l posit-ion throue'hout the vertical movement ot the switch. in its operated position relay lli clo circuits tor the slow acting relay Sti and :for the private magnet 39., which is also slow acting. The e-ncrgization t relay1 3G is `without function at this time, but the private magnet controls the usual cscapenient mechanism by means ot which the side switch is prepared 'tor its advance to second position. At the end ot the vertical iiiovenunit ot the switch, the slow acting relay 3ft -ifalls bach and breaks the circuits ot relay F56 andthe private magnet 39. Upon the deenergisation ot the latter, the side switch wipers 4&2 and itil are advanced to their second `positions by the operation ot the escapement.

'lfhe dial oli the calling device S may now be operated in accordance with the second digit ot the desired number, which is the digit 5. As beftore a` series of interruptions produced in the circuit ott' relays and 33, and these relays are accordingly deenergif/.eil intermittently live times. Relay 3l new sends a. series oit inrpulses to the rotary magnet il() over a. path which extends from ground by way oit armature 50 and its resting. contact, armature 53 and its working contact, vvindingiof relay 34, resting Contact et armature 58, and the said armature, Winding of the rotary magnet: el() and the side switch wiper 43, in second posit-ion, to battery. By the operation of the rotary magnet, the wipers F-75, inclusive, are rotated step by step and are finally brought to restin engagement with the particular contact set which corresponds to the desired major, or tliousands, group oit lines. This contact set assumed to be the one shown in the draw-- ing, and comprises banlr contacts 7 6451, in clusive. The slow actingl relay del is euergized in series with the rotary magnet Ll() the saine as in the previous case and closes cir cuits for relay 36 and lor the private magnet 89. The energization of the latter inagnet adjusts the escapenientin readiness to permit the said switch wipers to pass to third position when it dee-nergiaes. At YIdie end of the rotary movement ot the switch the slow acting relay Slt deenergizes and breaks the circuit ot the private magnet which thereupon deenergif/.es also and permits the side switch wipers to pass to their third position.

the operation described at the end ot the preceding` paragraph invariably result when a party line number is called, because oi" the tact that the set ot bank contacts in the test distriinitor, which is connected with, has its own test connector selector individual to it, and hence this set of contacts cannot be busy. However, in case a private or individual line number is called, in which iase the test connector required is reached directly by way oi the test distributor, it may be that such test connector is b sy and in such case it is necessary to prevent the seizure ot the connector at the test distributor and to give the calling wire chielt a busy signal. lt will be convenient to explain these operations. Now, it We assume, tor example, that the particular trunlr line shown at the right oit Fig. extends to a test connector, rather than to a test connector selector and ii we assume furthermore that this test connector is busy, then there will be aground potential on the test contact 79. Under these circun'n stances, when the 'slow acting relay 341; tails back after the rotary movement ot the switch is completed, a locking circuit is closed for the private magnet 39 which extends trem the grounded test Contact 79 by way ot the test wiper 73, side switch wiper 4t2, in second position, the lower winding oi 'test relay 35,normally closed contact springs controlled by armature 56, and the winding of the private magnet 39 to battery. The private magnet is thus locked in energized position and prevents the side switch wipers from going to their third positions. The heavy test conductors S2 and 83 are also held open at contact springs controlled by the private magnet, and are thus kept discon* nected from the wipers and 7 5. The test relay 35 is energized in series with the private magnet. This relay opens the rotary magnet circuit at its armature 58, and at its armature 59 connectie a lead trom the busy signalling machine to the lower side ot the test trunk, thereby placingl an audible busy signal upon the line which will be heard by the wire chief, and which will indicate to him that he has encountered a busy test connector. .at the same time relay 35 closes a circuit at its armature 57 tor the reversing relay 8O which, upon operating, reverses the conductors 9 and 11 of the test trunk as regards their connections to the windings ot relays 3l and 33. By this operation the direction of current iiowV in the lower winding of the electropolarized relay 202 is reversed, and the said relay is accordingly operated to close a circuit through the lresistance 203, and thence through the lamp 'L2 to battery. The lighting ot the lamp L2 at this stage of the' operation gives the wire chief a visual busy signal, suppleinenting the audible signal. He may now 'follow either ot two courses,` that is, he may release the connection by removing the plug` trom the jack, in which case the test distributor is restored to norn'lal as will be explained subsequently, or he may leave the connection` up until the 4desired test connector shall fhagve 4become idle. Assuming the latter course is followed, when the test connec- -toris freed, ground is removed Yfrom test contact .79 andthe circuit by which the test relayl 35 and private magnet 39 are betingr held energized is broken. VThe priva-te `magnet accordingly deenergizes, closes the heavy test conductors through to the wipers, and. permits the side switch wipers to pass .to third position, A and when the test relay 3,5 deenerg-izes it disconnects the audible ybusy signal, and also breaks the `circuit of the reversing relay 30. Upon the deenergization oit this relay, Vthe direction ot current yflow in the conductors ot the test trunk is restored 'to normal, vand the electropolariaed relay 202 is caused to retract its armature and extinguish the lamp L2. This notities the wire chief that the desired test v connector is now available and has been connected with, ,and 'he may, therefore, proceed to call the remaining digits.

After this digress'iou wc wil now return tothe establishment oit the connection under consideration, and explain its further progress. By the operation oit the test ydistributor. which has been describeththe `connection has been extended through as far as the Ytest connectorselector E, Fig. 6. lVlien the side switch wiper i3 oft i theV test listributor reaches its third position, a circuit is closed forre'lay 37 which energizes and extends the operatingcircuit through .to the impedance coil 38 in order to provide -tor tui-ther .energization of `the slow acting relay 3i, and atthe same time relay .3T prepares a point in the vcircuit ot' 'the .test wiper 72, and .also closes a bridge across Vthe wipers 7l and 74 at armature G4. By the latter operation a, circuit .is completed -tfor the windings ot' the line relay 100 o'tfthe test connector selector E, vand the said relay is accordingy tenergized and completes fa ,circuit for the .slow acting release relay ltll. Upon kcncrgaizinef in turn, rela-y itil connects ground to the lease trunk conductor S5, whereby the .connector selector ll 'is .made busy. i Alolay ltll also opens a lpoint in the circuit tot the release magnet 10.6 at rits armature ill?.y and at the same xarmature prepares a circuit for the rotary `magnet 105. It will be queried why it is ynecessary to ground the test contact 759 to .make the test connector selector E busy, inasmuch as according vto the previous explanation of the trunking arrangement the test distributor D is theonly switch which has access vto the test connector selector E. 'This is a pertinent question and the answer -is that it the trunking is arranged asdescribed there lis no particu`ar utility in grounding the test contact 79 when the test connector' selector is taken for use. The provisions tor grounding this test con ber of test distributors might bc incre;

Lthe test distributor D.

tact auses no harm htnvcvcr, and they render it possible to use switches such as thc .test connector sclcctor lil in alterna ti vc trunkino arrangement s without chan l fe.,

I t P* For instance, when thc testing facilities are increased ,the number ot'test distributors l) will increase liastcr than the number ol test connector selectors in any one group. Thus` the number et' test connector selectors ncad not exceed three no matter what size the sys teni is, but it is concci\fahl-:` that thc namcd to sin 0r even more.V In such case there would be two test distributors haring access to cach of the three test connector selectors in cach group. A

The wire chief may now opcralc thc dial ot' the calling dcvicc S in accordanrc with the third digit ol the desired uumhcr aud as a result another series ot interruptions arc produced in thc circuit ot reays ill and Bil ot As before. thc relay 3l sends an impulse ot' current` at cach dcenergization, through the slow actinggr series relay 34, and the said relay is energized and remains in operated position throughout thc transmission ot' the third series ot impulses. the saine as it did during thel transu'iissiou ot the tirst and second series. Since thiscircuit is completed by way ot' the coil Iii-. however, no further mechanical operation ot' thc` test distributor l) will take place` hut relay 3G and the private magney 39 arcoperated nevertheless, and the latter opens the test conductors 82 and 83 while the impulscsy arc being received. lt will be noticed that thc bridge across the wipers Til. and '7l which was closed at armature (34 of relay 3T iu chicles also the armature 5l ot relay 3.1, and it follows, therefore, that each time lrelay 2li deenergizes it will open thc bridge to causo the deenergization of the line relay l0() of the test connector selector lil. lt will hc seen then that the test distributor l) operates as a repeater utter it has itsclt been operated to repeat impulses to thc next switch taltcu ior usc, which in this case is thc afm'csaid test connector selector ll.

rlhe operation ot this switch may now hc described. At cach dccncrgization ol' thc line relay ltt), responsive to thc impulses which are repeated from the test distributor D, an impulse ot' current is transmitted to the rotary magnet 105 ovcr a path which extends from ground by way ot armature 109 and its resting contact, armature liz. and its working contact, winding ot the slow acting series relay 1.02, armaturc llti and its resting contact, winding oi the ro tary magnet 105, and side switch wiper `108 in its first position, to battery. lly the operation o't the rotary magnet 105, the wipers llBtl-ll. inclusive. arc rotated step by step and are stopped iu engagement with the particular set oi contacts in which is termilua ltlfl standing the fact. that the ott normal springs 157--159, inclusive, are shifted, which occurs at the tirst upward movement of the switch sli-aft. At the end of the vertical movement of the switch, relay 152 falls back and transfers the operating circuit to the rotary magnet 155.

The calling device may now be operated for the final digit in the desired number, which is the digit 8. A series of eight interruptions is thus produced in the circuit ot' relays 3l and 33 of the test distributor D, and these interruptions are repeated as before into the circuit of relay 100, of the test connector selector E, which in turn operates to repeat them into the circuit of the line relay 150 at the test connector H. Relay 150is, therefore, again deenergized momentarily a plurality of times and sends a ries of impulses to the rotary magnet 155 over a circuit which extends from ground y by way of armature 160 and its resting contact, armature 16:2 and its working contact, olf normal springs 157 and 15S, artnet-iure 163 and its resting Contact, winding of the slow acting relay 153, and the winding of the rotary magnet 155 to battery. By the operation of the rotary magnet wipers 17 0 172, inclusive, are rotated step by step and are finally brought to rest in engagement With the particular set of bank contacts in which is terminated the line of substation A, these `bank contacts being indicated in the drawing by reference character 173-175, inclusive. Relay is energized in-series with the rotary magnet and being slow lacting retains its armatures 164e and 165 attracted during the rotary movement and thus disconnects the wipers 170 and 172 until the switch is finished operating,vwhen it falls back and again connects up the Wipers to the heavy testing conductors.

Further operations at this stage depend upon whether or not the line of substation A is busy or idle. lt will be recalled that the circuit of the test distributor l) is such that after this switch has been operated the line relay 31 continues to send impulses to the slow acting relay 34 at the same time that it repeats impulses to the switches beyond. Thus, the said relay 34 is energized not only responsive to a series of impulses intended to operate the test distributor D, but also to the several series of impulses which operate the test connector selector Il) and the test connector H. It will be evident also that whenever relay'hl pulls up, circuits are closed for the slow acting relay 36 and the private magnet 39. lVith these facts in mind, the operations which take place, if the called line is busy, will ha readily understood.

If the line is busy when connection is established therewith by means of the testyconnector H, as explained in the foregoiini, the test wiper 171 will 1find a ground potential on the test contact .1711- and when the slow acting relay 34 in the test distributor D falls back at the end ot' the final series of impulses a circuitis completed t'or the reversing relay 30, which may be traced from the grounded test contact 1711 by way ot test wiper 171, conductor 160, test contact 133, test wiper 132, resting contact of armature 119 and the said armature. coinluctor 311, test contact 7S, test wiper T2, arniaturc 5l and its working contact, armature 55 and its resting contact, working contact; of armature 62 and the said armature. armature 6u and its working contact (slow acting relay 36 being' stillV in energized position), and the winding of the reversing relay 30 to battery. Upon energizing, relay 3() ci( branch of the above traced circuit which extends from armature 62 by way of the working contact of armature 65 and the said armature, armature 61 and its working contact, and the. winding of the slow acting relay 36 to battery. It may be explained that rela-y 30 pulls up and closes this branch circuit before the slow acting relay 36 has had time to deenergize following thc breaking of its initial energizing circuit by thc falling back of slow acting relay -t, and relays 30 and 36 are thus both held in operated position by the ground on the test contact 174 of the busy called line. Then relay 30 operates to reverse the direction of current flow in the lower winding of the electropolarized relay 202 in the test circuit in the usual inanner and this relay is, therefore, operated to light the lamp L2 and thus give the wire chief the visual busy signal. lt will be noticed, however, that no audible busy signal is in this case placed on the line, and indeed it would not be practical to do this inasmuch as the heavy test conductors are now actually connected with the two line conductors of the called line. Furthermore, the audible busy signal is unnecessary befause the wire chiefs head set is connected across the test conductors in series with the calling device, and by listening on the line he can at once ascertain whether it is engaged or not.

Finding that ay conversation is going on the wire chief may, of course. release the connection and try the number again later on, or he may again operate the calling device hey (l. D. in order to leave the connection under the control of the cleetrolmlarized relay 202. lf this latter course is followed, it will be evident that when the called line becomes idle and ground is removed from the test contact 174, the circuit of relays 30 and 36 of the test distributor D will be broken and the former relay upon deenergiznig. will reverse the direction of current flow in the lower winding of relay Q02 c L2 is extinguished, the wire chief being noti- .tied by this operation that the called line has become idle.

iin alternative method of holding the connection ou. the busy line which has an adantage in. that it does not :involve use of the testcircuit itself will now be explained briefly. .Assuming that in the foregoing example where the line of substation A was called and was found to be busy, the wire chief instead of proceeding as described may depress the holding button P associated with the trunk and withdraw the primary test plug from the jack J. The test circuit may then be used for testing other lines while waiting for the line of substation A to become idle.. The operation of the holding button P, which is of the self locking type, places ground on conductor 10, prepares a circuit for the 4lamp L, and closes a circuit for relay 7. Upon energizing, relay closes a local circuit for relays 31 and 33 of the test distributor D at armature 17, and at armatures 1G and 18 disconnects the heavy test conductors 82 and S3 from conductors 11 and 9, respectively, and connects them instead to the upper and lower windings of t-he battery feed relay 8. It follows that as long as the receiver is ofil on the called line, relay S will remain operative and will cause the lamp L to glow. Then the receiver is hung up, relay 8 will fall back and the lamp will be extinguished. It will be evident also that any operation of the switchhook or calling device. at the telephone will cause the lamp to flash so that t-he wire chief has complete supervision over the line during the time that the holding button is in depressed position.

Having explained the operations which take place when the called line is busy, we will now consider what occurs when the linel is idle, it being immaterial whether we consider that the line is idle when called, or becomes so some time after the connection has been established. In either case, when the slow acting relay 36 of the test distributor D falls back acircuit is completed which extends from ground by way of the resting contact of armature 00 and the saidy armature. arnuiture 62 and its working coi'itact, resting contact of arinature 55 and the said armature, working contact of armature and the said armature, (est wiper 72, (est contatiit 79, conductor del, armature 119 and its resting contact', test wiper 132, test contact 13?, coi'lductm 169, test wiper 171, test contact 174, private normal conductor `177, winding of the cut off relay 179, and the winding of the rotary or stepping magnet 180 of the line switch C to battery. Bv the closure of the above circuit, a ground. potential is placed on the test contact 174 to make the line busy in the usual manner, and at the same time relay 17 9 is energized and clears the line of substation A of its normal battery. and ground connections in the line switch C, lt may be explained at this time that relay 170 is operated only about half way because of a mechanical locking` device controlled by `the line relay 181 and the Wipers of the line switch are not connected up.

Having completed the connection to the line which it is desired to test, the wire chief may now restore the calling device key C. D., thereby disconnecting the calling device S from the test circuit and again closing the tip and ring conductors. When in normal position, the calling device key opens the energizing circuit of the polar* izing` winding of rela 202 and also closes a circuit through the sleeve of the primary test plug, which may be traced from ground through the winding of relay 201, contacts of the calling device key C. D., serially related contacts in the B. C. O. key, the conn. release key, cord reverse key, and the release key, sleeve `of the primary plug, and the sleeve of jack J, winding of relay 5, and the winding of relay 6 to battery. Upon `the closure of the above circuit, relays 201 `and 5 are energized, but relay 6, vi-*Inch 1s of low resistance and which is marginally adjusted, does not pull up. Relay 201 closes the tip side of the test circuit over a path which excludes the lower winding of relay 202, and also closes a circuit for the lamp L2, which now becomes a supervisory lamp. Relay 5 in the outgoing trunk circuit closes a local energizing circuit for relays 31 and 38 of the test distributor D at armatures 13 and. 1.4i, at the same time disconnecting these relays from the heavy test conductors 11 and 9. It will be seen now that as long as the sleeve circuit remains intact, the connection will be held by the local circuit closed by relay 5 in the outgoing trunk, while the tip and ring conductors of the test circuit are extended over direct metallic conductors to the two sides of the subscribers line, respectively.

If it is desired to talk to the subscriber, the ringing key may now be operated momentarily in order to ring his bell and call him to the telephone. This act simply opens the two sides of the test circuit and connects a ringing current gei'ierator in bridge thereof in the usual manner. The listening key is now thrown and also the repeating coil eut-in key (l. (l. l. By the operation of the listening key the wire chiefs head set is connected. across the tip and ring conductors of the test circuit in series with the condenser 215, while the listening key and the R. C. C. l. key together connect the battery feed relay 200 across the tip and ring conductors also in order "to-supply t'alfkil-ig` current to the transmitter at the subscribers telephone. The circuit of'tliie vwire chiefs telephone set will be sufficiently obvious without explanation,

but it maybe advisable to trace the connections for the relay 206 briefiy The battery supply flows from ground by way of the upper winding ot' relay 206, the upper righthand winding ot repeating coil R, and through serially Vrelated."contacts ol the R.

.30. C. Yl. 'and' listening keys to the normally closed tip side ot the test circuit. thence by way of the heavy test conductor to the subscribers station, and back over the ring slde koat the test circuit lto the listening key,

exchange battery is connected to conductor 205,V thus shunting out thev supervisory lamp L2 and extinguishing it.V The subscriber may now be engaged in conversation in the usual manner.

In case the Wire chiefis busy talking to someone else and does not wish to leave the listening key on this particular test circuit in operative position, While waiting for the called subscriber to answer, he may operate the ground key instead of the listening key. This kgrounds the tip side of the test circuit andV affords a return path for the battery supplied through the lower Winding of relay 206 tov thercalled subscribers transmitter when he answers. Relay 206 is Vthen operated by means ot' its lower winding alone and eXti-nguishes the supervisory lamp Lg as just-described. This notifies the wire chief that the subscriber has answered and he may then operate his listening key and restore the ground key.

It will be convenient now to explain how the Vconnection isA released. 'Ttit is desired to release the entire connection without withdrawing the test plug from the jack of the outgoing test trunk, the release key is operated for a. short interval. This opens the sleeve circuit and causes relay in the outgoing trunk to be deenergized. thus breaking the local energizing circuit for relays 31 and 33 in the test distributor D and again connecting these relays to the heavy test connectors 11 and 9, respectively.

Assuming now that all the other keys in the testV circuit are in normal position, there `will be no circuit closed to maintain vthe Said relays 431 and 33i energized and they will fall back. Relay 3lV brcaly's the operating circu-it extending to the test connector selector- E, and also breaks the circuit of the slow acting release relay 32. lVhen the latter relay falls back it closes a circuit for the release magnet 4st which restores the test distributor l) to normal position in the well known manner. At the test connector selector E when the circuit of the line relay 100 is broken, this relay falls back and breaks the circuit of the slow acting release 'relay 101, and, upon deenergizing, the latter relay closes the circuit ot the release magnet 106. The operation of release magnet 1.06, of course, restores the connector se-I lecto-r E to normal also. The line relay 100 on deenergizing Ibreaks the circuit of the line relay 150 of the test connector ll, and this switch is accoi-dingly restored to normal by the operation of release magnet lG, whose circuit is closed in an obvious manner by the joint action of relays 150 and 151. Thus, all the test switches in use are returned tol normal position and are ready to be rebperated to connect with the same or another line.

Sometimes it is desirable to release the test connector selector and the test connector without restoring the test distributor as, for example, in case it is desired to test another line in the same group. This can be accomplished by the operation of the conn. release key. lhen this key is operated, the exchange battery is connected by way of resistance 205 to the tip and'ring sides ot the test circuit simultaneously, while at the saine time the sleeve circuit is opened. Relay 5 in the outgoing trunk circuit accordingly falls back, breaks the local holdingl circuit for relays 31 and 33 of test distributor D, and connects these relays to the heavy testing conductors. Sinie both sides of the test circuit are connected to the ungrounded pole of the battery, relay 33 will be held energized, but relay 3l is short circuited and will fall back. Relay 33 holds the slow acting release relay 32 energized in order to prevent the release of the test distributor D, while relay 3l breaks the operating circuit of the test connector selector E, and thereby causes the test connector selector and test connector to be released and restored to normal, as ncviously described. It will he observed that relay 3l closes a circuit through the slow acting relay 3l. which in turn cuergizes, and closes a circuit for the private magnet 39. The operation of' the private magnet at this time opens the heavy testing conductors and prevents the application of battery potential to other lines while the test connector selector E and the test connector H. are returning their wipers to normal position. The conn. release key need be operated only for a brief interval, and after itv is restored `tonormal the calllll iframes ing devine key (l. D. may be operated lor connected through resistance 205 to the scction which includes relay 201.. rlhe grounding ot the sleeve oi the plug causes the marginally adjusted relay G to energize and the local energizing circuit for relays 3l and 88 of the test distributor D is broken at the normally closed contact springs controlled by armature 15, while at the same armature ground is connected to the winding of relay 31. It follows that relay 31 is maintained energized, while relay 33 is permitted to :tall back. The deenergization of relay 33 disconnects ground from the test wip ir 72 of the test distributor switch D and thus breaks the circuit of the cut orf relay 179 of the line switch C. By means ot the volt milarnmeter, the wire chief may now test the two sides of the subscribers line for battery and ground, respectively, in

manner which will be explained subsequent- 'f ly, or he may connect his calling device S across the conductors of the test circuit and call out through the automatic exchange by way of the subscribers individual. line switch C.

rllhe standard routine tests for line troubles are performed in substantially the saine manner as in ordinary practice, and hence will reqiiire only a cursory discussion. Considering rst the method of testing .for a ground, this test may be performed either with the volt meter scales oit the volt milanimeter, or with the milainpeii'e scale. With all the keys in the test circuit at normal the 100,000 ohm volt meter winding of the volt milammeter is connected from the ring side 4of the test circuit to ground in series with the 100 volt testing battery. The circuit may be briefly traced from the ring side oi' the testing circuit at the R. C. C. l. key by way of contact of V. M. reverse key, contact olf relay 207, contacts of relay 208, through the 100,000 ohm winding oi' the -volt milani* meter, contacts ot the scale change key, contact ot relay 209, contacts ot the R. C. C. l. key, contacts o'l the F. E. M. F. key, contacts of the scale change key, and through the 80 and 20 volt batteries in series to ground. Under the above described circuit conditions, it will be seen that it there is a ground on the ring side of the line the needle ot the volt milammeter will be deiiected and the deilection is read on the 120 volt scale. rllhe tip side ot the line may be tested for ground by operating the reverse key.

ln case it is desired to measure the resistance ot the ground with the volt milanimeter according to well known methods, it is desirable to use that winding of the volt milammeter whose resistance most clearly approximates the resist-ance of the grouniil in order to secure the maximum accuracy in the result. It the ground is of relatively low resistance, therefore, it will be advisable to use either the 20,000 ohm volt meter winding, or the 1,000 ohm volt meter winding, which may be substituted 'for the 100,000 ohm volt meter winding by the use ol the scale change key. l/Vhen thrown in one direction, this key connects the 20,000 ohm winding in the circuit and when thrown in the opposite direction it connects the 1,000 ohm winding in the circuit. liVith the scale change key operated in either direction the volt testing battery is used, and the detiection is accordingly read on the 241 volt scale.

lf desired, tests for grounds may be made with the 10 ohm milanimeter winding ot the volt milammeter, using the 4180 milanipere scale. ln testing for a ground on the ring side ot the line in this way, the lt. C. C. l'. key is operated which connects the 10 ohm milammeter winding from the ring side of the line to ground in series with the lower winding of relay 206, and the regular exchange battery over a path which may be biely pointed out as follows: from the ring side of the line at the listening key, by way of resistance 211, contacts ot the R. C. U. l. key, contacts of relay 207, contacts oi' relay 208, 10 ohm inilamnieter winding, contacts oit relay 208, contacts oiirelay 207, contacts of the V. M. reverse key, contacts oi the lli. C. C. l. key, lower rightl'iand wind ing oi repeating coil it, lower winding oi relay 200 and the exchange battery to ground. lilith these circuit connections it will be evident that .it the ring side of the line is grounded, the needle of the volt milammeter will be deflected accordingly. The tip side of the line may be tested in :i similar manner by using the reverse key ln order to test a line tor a short circuit the procedure is as t'ollows: The .line is first tested for a ground to insure that it is clear in this respect, and then the tip side ot the line is grounded by the operation oi the ground key, after which the ring side ot the line is tested for a ground, described in the 'foregoing paragraphs. 1t will ohvious that it the line is short. circuited the ground which has been placed on the tip side ot the line will he detected by testing the ring side. 1t will be unnecessary to state that test may be performed with either ot the volt meter scales, or with the milammeter scale.

Continuity tests are performed according;` to the usual methods, depending on the normal circuit condition ot the line. It the line is supposed to be electrically continuous through a bridged ringer, drop or other device, it will be tested tor a short circuit, and the size or resistance ot the short will inoicate whether or not the circuits are in their proper condition. lt there is a condenser normally included at the station on the line there, oit' course, will be no deflection ot the rolt inilamrneter when trie line is tested tor a short circuit, and the usual method ot testing a line of this kind 'tor continuity is to rapidly operate the revcrsekey three or 'tour times. It the line is 0. li., the charging' and discharging ot the condenser at the sul:- scribers station will cause momentary del-lections or kicks7 ot the volt meter needle which indicate that the circuit is intact.

Another test which is quite freqiunitly used is the test for foreign battery on the line, which condition may be due to eros with other circuits. lnorder to make this test the E. M. F. key is operated, wl'iwh connects the 100,000 ohm winding` ot the volt milammeter trom-the ring); side ot the test circuit to ground over the following* path: from the ringl side ot' the test circuit at the R. C. C. I. key by way ot contacts ot thc V. M. reverse key, contacts oit relays 20T unil 208, 100,000 ohm winding` ot the roltv meter, contacts ot the scale change key, cf tacts of relay 209, contacts ot the (l. key, contacts ot the F. E. M. l?. key, and con-- t-acts of the V. M. reverse key to 2f., Gund will be evident that with the volt inilainnieter connected in the above circuit, the needle wi il be deflected in oase there is a battery potential on the ring side ot" the line. lt the pir larity ot t-he :foreign battery is such that it gives aneeative reading ot the rolt init imeter the V. M. reyerse key is used, which would operate simply to reverse the connections to the 100.000 ohin winding ot the volt milammeter without othcrwis3 changing' the circuit connections. The tip side oit the line is tested for foreign battery the saine way, except that the reverse key is operated.

It the line under test is tound to be crossed with another telephone line, a yenient method for making accurate and speciiic tests of the cross is to connect the sccondary testing` circuit with one ot the lines. while the liriniary testing circuit is connected with the other line. The tip and ring' sides of the secondary testing circuit n ay now be grounded successively b i means ot the ground and reverse keys, while at the same time the tip and ring sides ot the line at the primary testing circuit are tested tor :ground in the usual manner. It the two lines are crossed the ground which placy .L on one of the lines at the secondary test cilIV cuit should be picked up on thc line which under test at the primary test circuit.

The breakdown test key is used in mak ing insulation tests. This is a special key which is illustrated diagraminatimlly in the drawings as comprising the rotatahh shaft 223 and the two cani wheels 220. 522i. and 222, ach of which controls contact springs. then it is desired to test. the insulation of a telephone line with which thc test circuit is connected th'.` ln'ealnlown test key operated manually und utter :i nioineut is restored to no1-unil. The construction ot the key is such that a numhcr ot" circuit changes are produced in u dclinitc sequence as follows:

First., the contact, springs controlled by cam 220 are closed, thereby completing; :1 circuit for relays 210, 20S, and 200 in series and these relays are energized. Vhc operation ot relay 210 connects the ringl side ot the test circuit directly to ground, while by the joint action ot all three relays the tip side of the line is connected to ground through the 96,000 ohni resistance coil which is associated with the breakdown test key. The latter Circuit may be traced briefly from the tip side of the test circuit at the ground key b y way of contacts ot relay 20S. the 10 ohm niilannneter windingr ot the rolt inilammeter, contacts ot relay Q03. contacts of relay 210, through the 90,000 ohni resistance coil and through the normally closed Contact springs controlled by cani 22'] to ground.

Second, thecontact springs controlled by the cam wheel 221 are operated. thereby connecting' the l0 ohm inilanunetcr `winding` ot the volt milamnieter 'troni the tip side oli' the line to `ground in series with thc 96,000 ohm resistance coil and the 200 rolt battery. the circuit beine' briefly traceable from the tip side ot the line at the ground key by way ot contacts ot relay 108. the I0 ohm inilannneter winding. contacts ot' rclay 208, contacts ot relay 2'10d the 00.000 ohm resistance, the now closed contacts controlled by cani wheel 221, and the 100 volt. volt and 20 Volt batteries. all in series, to ground. The inclusion ot' the high resistance provides tor gradually charging the condens-er, or condensers, included in thc ringing circuits at thc telephone substations and thus effectively prevents thc belley Jfrom tapping.

Third, theA Contact springs controlled by the cani wheel 222 are closed with the result that the 96,000 o-lnn resistance is short circuited, and the 200 volt battery is thus` con nected direct to the line in series with thc l0 ohni inlammeter winding. It there is any detectl in the insulation ot the line it is obvious that a deflection ot the needle ot the cord reverse keys.

with the primary test circuit by means oi' the cord reverse key in the secondary test circuit. This is very convenient in case a connection is established by means of the primary testing plug for example and it is lfound the. character ot' the trouble on the line requires the use o'l some testing key in the secondary test circuit which is not duplicated in the primary test circuit. Obviously in a case of this kind it will not be neces lary to change the testing plug, but: the proper testing circuit may be immediatelyy associated with the testing plug which is already in use merely by operating the two cord reverse'keys. .Beginning at the end next to the secondary test plug, the release key, the conn. release. key, the B. C. t). key, the C. D. key, the ringing key, the reverse key, the ground key, the monitor key, and the listening key are duplicates ot the like named keys in the primary testing circuit and are provided for like purposes, which have already been described. It may be stated iturthermore that the sleeve circuits and thel supervisory circuits associated with the secondary testing plug are the same as those associated with the primary testing plug.

The howler key is used for signalling a subscriber who has left his receiver off and when operated causes a high frequency induced current to be projected out over the line, which makes a sound in the receiver which is audible at some distance therefrom. Suppose, `for example, that a line is reported to the wire chie't as being permanently busy by reason oi the receiver having` been lett off. The wire chief will use a secondary `testing circuit and by inserting the secondary test plugl in the jack otl an outgoing test trunk he can establish connection with the line in question in the same manner as was previously explained. As soon as the line is connected with and the calling device key C. D. is restored, the battery supply relay 232 is energized and shunts out the supervisory lamp L3, which would otherwise be lighted by the energization of relay 230 in the sleeve circuit. The Wire chief may now listen on the line in order to confirm the reported nature of the trouble, and will then operate the howler key. The operation of this key disconnects the two leads which extend down to the primary cord reverse key, connects the lefthand windings ot the. repeating coil R* in series with the secondary winding of repeating coil R5, and closes a circuit for relay 235 which includes the movable contact lever 240 in its normal position, the working contact and lower armature ot relay 232, and the uppermost contact springs of the key. Upon energizing, relay establishes a locking circuit for itself at itsl lower armature and at its upper armatureI prepares a circuit for relay 234. Relay L55 also closes a circuit by which the high speed interrupter I is connected in series with the primary winding ot' the induction coil or transformer R5. The movable contact lever 2210 now shifted from its normal position to some other position in orderI to include a suitable number oi turns ol the secondary winding of the induction coil Rf in series with the letthand or primary winding ot' the induction coil R4. As a result of these operations a high frequency induced alternating current is transmitted over the line and through the receiver at the subscribers station, where the subscriber is notiiied by the familiar tone or howl in his receiver that he has forgotten to hang it up. lVhen the receiver is replaced relay 232 is deenergized and closes a circuit for relay 234, which upon energizing, establishes a locking circuit for itself and opens the circuit ot the interrupter I. The howler current is thus permanently disconnected regardless of whether the subscriber again removes his receiver or not. The deenergimv tion of relay 232 also causes the supervisor)7 lamp L3 to be lighted, which notities the wire chief that the receiver has been replaced and he will then restore the howlcr key to normal.

It will be observed that the tip and ring sides otthe secondary test circuit are normally connected through the windings of the repeating coil .R4 with the windings ot' the battery feed relay Q32. In order to disconnect the battery teed relay when the secoudary test circuit is being used in conjunction with the primary test circuit in testing for crosses with other lines. the l. (l. key is provided. rfhis key may also be used when the wire chiel is talking on a toll line, or some other kind of line. where the party at the distant end has an independent supply of transmitter battery.

The sounder, shown at the upper righthand corner of Fig. 2, may be connected across the tip and ring sides of the secondary test circuit in series with the battery by means of the sounder key, and is used ior a variety of purposes. For one thing it is rather useful in giving the wire chief an audible indication of the ieoccnrrence of swinging short circuits, or grounds. Another casc in which it is used frequently is when a repair man is working on a subscribe1"s line and is instructed to call ltlf) llo the wire chief tor a test. 4It the sounder is lett across the line it affords a convenient method by which the repair man can signal the wire chiel. The sounder is also used to some extent for gauging the regularity of a series oit interruptions produced by a subscribers calling device.

Tests ot the subscribcrs calling device, or impulse sender, however, are usually made with the impulse test key. The conductors 244iand 245 associated: with this key extend to the tirst oi' a series ot automatic switches, and when the key is operated the tip and ring sides ot the testing circuit are extended by way ot th said conductors, respectively, to the line relay of this switch, which may then be operatedi by the sub-y sc-riber at the station whose calling device is to be tested. The usual procedure is for the wire chiel' to request the .subscriber to call a certain number, and it he agrees, the wire chief will immediately restore his listening key and throw the impulse test key. The wire chief will then observe` the opera tion ot the switches in response to the operation of the calling device at the subscribers station and it any trouble is de tected,` he will take the necessary steps to correct it.

The foregoing explanations while by no means exhaustive are believed to cover the tests most commonly used with suiticient particularity to enable them to be readily performed, while the apparatus has been described in suiiicient detail to enable those skilled in the art to perceive the variations from prescribed methods' which are possible, and to perform other similar tests which it has not lbeen considered necessary to` describe. It will be seen that a highly organ ized system of wire chiets testing circuits has been designed which includes many new circuit arrangements and producing many new testing and operating features, all et" which add very appreciably to the` commercial value of such systems.

Having described my invention, what I consider to be new and desire to have protected by Letters Patent will be pointed out in the appended claims.

Vilhat I claim is:

`1 In. a wire chiefs testing system, a test circuit terminating in a three conductor cord and plug, a jack ending test trunk and a. series oft automatic switches tor extending said test circuit into connection with a subscribe-rs line, a calling device adapted to control said switches over the tip and ring sides of the test circuit in series, a busy and supervisory signal controlled through the sleeve of said plug and jack, and keys and associated devices in said test circuit for performing a series ot tests on a connected line.

2. In a wire chiets testing system, two test cir-cuits each ter inating in a manual meter tests ot subscribers lines, a secondary:

test circuit also terminating in a manual cord and plug, keys and other devices associated with said secondary test circuit 'for making line tests not requiring a volt-meter,

and a. cord reverse key in leach test circuit` whereby the two test circuits may be interchanged with respect to said plugs.

4. In a wire chiets ltesting system, two test `circuits each terminating in a manual cord and plug and each being provided with keys and associated testing apparatus, an outgoing test trunk ack and a series ot automatic switches whereby either test circuit may be extended into connection with a subscribers line, and a cord reverse key in each test circuit whereby the two test circuits may be interchanged with respect to said plugs.

5. In a wire chiefs testing system, a primary test circuit terminating in a manual cord and plug, keys and a voltmeter associated with said test circuit for making volt-meter tests of subscribers lines, a secondary test circuit also terminating in a manual cord and plug, keys and other devices associated with said secondary test circuit tor making line tests not requiring a voltmeter, an outgoing test trunk jack and a series of automatic switches whereby either test circ-uit may be extended into connection with a subscribers line, and a cord' reverse key in each te-st circuit whereby the two test circuits may be interchange-d with respectto said plugs.

6. In a wire chiets testing system, a test circuit comprising a plurality ot keys and associated apparatus for testing subscribers lines, a series of automatic switches controllable from said test circuit to connect the same with a subscribers line, a lamp signal, means for controlling` said lamp as a busy signal tonotity the wire chiet during the establishment ot a connect-ion that a busy switch has been encountered, and .means operative in case the connection is completed for controlling said lamp as a supervisory signal to notity the wire chief when the subscriber answers.

7. In a wire chiets testing system, a test circuit comprising a plurality ot keys and associated' apparatus tor testing Subsc ibers lines, a series of automatic switches controllable from. said test circuit to connect the same with a subscribers line, means tor transmitting visual and audible busy signals to the wire chietl during the establishment of a connectionto notify him that a busy switch has been encountered, means Jfor conipleting the connection to the desired line whether it is busy or not, and means for giving the wire chief a visual busy signal if the line is busy.

8. Ina wire chiets testing system, a testcircuit comprising a plurality of keys and associated apparatus for testing subscribers lines, a. -series ot automatic switches control-led' from said test circuit to connect the same with a subscrib.e1"s line, a test wiper in the final switch ot said series for testing the line to determine whether it is busy or idle, and a test relay in a. preceding switch controlled over said test wiper for giving the Wire chief a busy signal.

9. In a wire chiefs testing system, a test circuit comprising a Jlurality of keys and associated apparatus tor testing subscribers lines, a series of automatic switches controllable trom said test circuit to connect the Same with a subscribeus line, a test wiper inthe linal switch ot' said series for testing lthe line to determine whether it is busy or idle, a test relay in a preceding switch controlled over said test wiper, and means controlled by said relay for giving the wire chief a visual busy signal.

10. In a wire chiefs testing system, a test circuit comprising a. plurality of keys and associated apparatus for testing subscribers lines, a seriesot automatic switches controllable from said test circuit to connect the same with a subseribers line, a. test relay in the first switch ot said series, means controlled by said relay for giving .the wire chief a ybusy signal, a circuit for operating said relay during the establishment of the ,connection in case the second switch is busy,

and `another circuit for operating said relay in .case the third switch is busy.

1l. In a wire chiets testing system, a test circuit comprising a plurality of keys and associated' apparatus for testing subscribers lines, a series of automatic switches controllable from said test .circuit to connect the same with a subscribers line, and means i-n said test circuit for controlling the release ot said switches whereby the wire .chief can releaseJ all of said switches or only part of the said switches at his option.

12. In a wire chiets testing systeima test circuit comprising a `plurality ,o-:t keys and associated apparatus tor testing subscribers lines, a series ot automatic switches controllable from said test circuit to connect the same with a subscribers line, means in said switches tor energizing the cut olf relay Of the subscribers line when the line is connected with, and means in said test circuit for deenergizing said relay while maintaining said switches in operated yposi-tion.-

13. An automatic tru-liking system in .which 'the switches lare `operated y exclusively under directive control and comprising; tesi distributor switches. tesiccnnccor selector switches accessible to said i 'lributor switches, each of the latter switches being individual to one ot theI former, and lest connector switches cach ot which is accessible to a plurality ot said connector selector switches.

14. An automatic trunling system in which the switches are operated exclusively under directive control and comprising test distributor switches, test connectors and te. connector selectors accessible to said test distributors, each test connector beingl accessible in common to all ot sai-:l l is1il,-utor switches while each test connector lector is accessible to only one oi said distributor switches, and other test connector switches each of which is accessible to a plurality ot said test connector selector' switches.

l5. In a telephone system, a manual switchboard, means including a trunk line outgoing from said board and a train of scrially related automatic switches tor extending a connection to a subscribcifs line, a circuit tor energizing' the cut-olf relay ot said subscribers line, said circuit including a wiper in each of said switches, and means in the rst of said switches controlled from said board for opening said circuit to deenergize said cut-oil relay.

16. In a telephone system, a manual switchboard, means including a trunk line outgoing from said board and a train of serially related automatic switches for cx tending a connection to a` subscribei"s line, a circuit for energizing the cut-olf relay ol" said subscribers'line, said circuit including a wiper in each ot said switches, a jack in which Said trunk line terminates at said board. and a relay controlled over tbe sleeve of said jack for opening said circuit to deenergize said cut-oil relay.

17. In a telephone system. a manual switchboard, a trunk line outgoing from said board and having two branches,ia train of automatic switches controlled over the tir/st of said branches to extend the second of said branches to a subscribcrs line and a relay at the junction ot said branches controlled from said board 'for disconnecting the -said irst branch.

1S. In a tele-phone system. a switchboard, a trunk line outgoing trom said board and havingr two branches. :1 train of automatic switches controlled over the first, of said branches to extend thc second. .of said branches to a subscribers line, a relay in said trunk line controlled from said board for disconnecting the said first lnanch, and a local circuit controlled by said relay for maintaining said switches 4in operated position.

lSigned by me at `Chicago, Cook County,

manual Illinois, this 31st day of. January` 1,921.

.WILLIAM A, BESSON. l 

